Virtual lung for chest physiotherapy – VirtualChest

Lung's secretions capture the external pollutants (either chemical or biological) and the natural motion of secretions up the bronchial tree lead these pollutants outside the lungs. Motion of secretion is achieved thanks to two main mechanisms: the beating of cilia standing on the epithelium cells, and cough. However, these mechanisms are not mature in children and can be altered by age or by common pathological conditions like cystic fibrosis, bronchiolitis, asthma, COPD, etc. Mucus stagnation in the lungs increases the risks of infection and obstruction of the bronchi. Chest physiotherapy (CP) is then used to help the secretions to get out whenever mucus stagnation occurs. CP is based on pressures applied on the thorax. Recently, controverted studies have criticized CP efficiency and its potential risks have been highlighted. Because the discipline is empirical, the debates cannot be constructive as of today. These questionings could have serious consequences in term of public health and economy at a time when social securities aim to reduce their spending. The objective of this interdisciplinary project is to characterize scientifically CP techniques efficiency and comfort for the patient. We will define two indexes in order to bring scientific arguments to the debates, and we will propose improvements to current CP techniques. To reach this objective, we will develop an integrated, patient-dependent, numerical model of the biomechanics of CP. Our project focuses on child cystic fibrosis whose treatment involves frequent CP and is well structured in France with the CRCM centers. CRCMs centralize both patients and data from specific locations.

This project decomposes into two complementary components.

The first component aims to setup the in silico integrated model of CP. We will develop the mathematical and numerical models of the different biomechanical aspects and scales of CP. We will search on how to optimize CP effects at each modeling levels, in order to get a clear understanding on how to optimize a whole technique. Several physical phenomena are complex and their modeling will be based on experiments in order to get the most accurate behavior for the integrated model. For each patient, we will map CP-induced thorax displacements -measured in the other component of the project- on a 3D reconstruction of the patient thorax from CT-scans. Thus, we will be able to deduce lung’s wall displacements. Then mucus motion in bronchi and lung inner constraints will be computed from a biomechanical multi-scale model of the patient lung. These data will then allow computing the two indexes.

The second component of the project aims to acquire data for the model input and validation, still with a patient-dependent approach. For the first time, a full set of concomitant CP biomechanical and medical data will be acquired. We will use a specific protocol and new, dedicated, measurement systems developed in the frame of this project. We will build an initial database with patients from R. Debré hospital CRCM. With this first dataset, we will validate our protocol, instruments and model, then we plan to expand our dataset with other CRCMs with which we are already in contact. The data acquired in this second component of the project will form a strong basis for the numerical model validation. Then, the numerical model will improve greatly our understanding and interpretations of the data acquired, it will allow to validate the indexes proposed and finally will make it possible to propose improvement to current CP techniques. In term of perspectives, the model and protocol developed in this work will be used to extend our study to a wider range of patients and to other pulmonary pathologies. In term of industrial development, we are in contact with several industrial partners who are interested in our future tools in order to evaluate and optimize the efficiency of their medical devices for CP.